The present invention relates to an automatic indexing chuck for angular step-by-step moving of jaws.
As is known to those skilled in the art, automatic indexing chucks allow, with a single load and a single locking, machining of parts with faces which are mutually orthogonal, or more generally angled to one another, and this occurs by virtue of the action of fluidodynamic and/or mechanical systems adapted to provide a step-by-step angular rotation of the jaws around the radial grip axis and a locking thereof in the subsequent work positions.
Some known indexing systems are based on the use of complicated devices which employ step-by-step angular indexing mechanisms and stop mechanisms for performing rotation and locking which are generally differentiated and operated by fluidodynamic pistons which require accurate synchronization by means of complicated hydraulic and/or electric controls.
More recently, in the attempt to simplify the above described known indexing mechanisms, a device has been proposed and produced which makes use of a single reversible-stroke piston adapted to provide rotation of the so-called indexing or dividing pivot (a prismatic portion of the jaw's supporting pivot) for one direction of the work stroke and locking of said pivot for the reverse stroke direction.
The piston is provided with differentiated active pushing and locking surfaces which act on corresponding faces of a prismatic dividing pivot.
This known and more recent indexing device, described in the Italian patent application No. 20415-A/83 dated Mar. 31, 1983, though simplified, also has remarkable disadvantages, mainly residing in the complicated structure of the piston which bears both pushing and locking surfaces and the corresponding complicated profile of the prismatic portions of the dividing pivot: both these mechanical elements require accurate machining with very small tolerances for a correct operation of the device.
Another serious disadvantage of this known device resides in the bulk of the piston, the axial extension whereof--due to the bidirectionality of the work stroke--is at least double of that of the pistons of the preceding multiple-piston indexing devices. This increases the dimensions of the chuck with a considerable and undesirable increase of the inertial mass thereof. Moreover, the greater axial extension of the piston requires, mechanical rigidity being equal, increased cross sections which penalize further dimensions and inertial masses.
Further disadvantages of this known device reside in the relative slowness of the angular indexing movement, and in the fact that between end of rotation and beginning of locking, coupling between the dividing pivot and the piston is totally released, both disadvantages deriving from the change in direction of the work strokes of the single piston.